The present invention is concerned with the first stage of preparation of compost for commercial cultivation of mushrooms. This stage is commonly referred to as the "pre-wet cycle".
In the pre-wet cycle, the compost ingredients are positioned on a concrete pad and are repeatedly mixed, aerated and wetted with water at regular intervals over the duration of a retention period. Heretofore this has commonly involved:
placing bales of straw in a windrow on the pad; PA1 depositing nutrient, such as horse and chicken manure, on the bales in pre-determined amounts or proportions using a front end loader. (Typically one might have a formulation of 75% straw, 20% horse manure and 5% chicken manure); and PA1 periodically using a front end loader to turn the windrow to induce mixing and aeration. The objectives are to uniformly distribute the ingredients and to convert the mass to a "fluffed up" state so that air can penetrate the mass to assist contained bacteria in carrying out conversion to compost. The fluffed up mixture is wetted thoroughly by spraying it with water. This is done with the objective of adding as much water as the mass can absorb without significant runoff. The bacteria won't attack the straw if it is not moist. However, if there is excessive water run-off, nutrients are lost. It is then necessary to recycle the run-off water. PA1 (a) establishing an initial windrow of vertically layered ingredients provided in the proportions desired for producing pre-wet cycle compost; PA1 (b) milling across substantially the entire end face or cross-section of the windrow, at one time, and advancing longitudinally of the windrow, the milling being conducted along a forwardly-inclined plane at an acute angle relative to ground, whereby a cross-section of the windrow is removed without substantial cave-in of the unmilled portion of the windrow, and propelling the milled material upwardly and rearwardly so that it drops to form a vertically blended, loose, laterally extending product; PA1 (c) conveying this product laterally of the initial windrow and delivering it to a transfer point; PA1 (d) elevating the product from the transfer point and discharging it to form a new windrow extending in the same direction as the initial windrow; PA1 (e) wetting the vertically blended, loose product, preferably as it is conveyed laterally and elevated; and PA1 (f) periodically repeating steps (b), (c), (d) and (e) on each new windrow to produce a substantially homogeneous pre-wet cycle composting mixture. PA1 layering the ingredients to ensure that their proportions are correct within a cross-section; PA1 progressively milling substantially the entire vertical extent of the layered windrow at one time, so that the initial proportions are retained in the milled product; PA1 milling along a forwardly-inclined plane so that cave-ins are minimized, as such cave-ins would result in variations in concentration of ingredients; PA1 mixing the ingredients by propelling them upwardly and rearwardly so that they drop and collect in a now well-mixed, loose, transverse assemblage or "product" whose composition reflects the composition of the initial windrow in the vertical direction; PA1 preferably conveying the milled product laterally and delivering it to a transfer point that is advancing along the line of the initial windrow. This action provides cross-mixing, to cope with potential side to side variation in ingredient distribution (more preferably, the linear assemblage of milled material is conveyed laterally and inwardly from its ends to a central point generally coincident with the axis of the initial windrow); PA1 elevating the milled, mixed and cross-mixed product and depositing it to form a new windrow; PA1 preferably wetting the linear assemblage while it is in a "fluffed up" or loose state in the course of being propelled rearwardly conveyed laterally and elevated; and PA1 repeating the process with each new windrow until the pre-wet cycle is complete. PA1 a mobile, driven, wheeled carriage; PA1 a plurality of toothed drums, rotating in the same direction and arranged along a forwardly inclined plane, said drums being adapted to substantially cover the entire cross-section of the windrow, for milling longitudinally substantially the entire cross-section at one time and propelling the ingredients upwardly and rearwardly, so that they drop and mix to form a transverse assemblage or product; PA1 means for receiving the assemblage and conveying it laterally to deposit it at a transfer point, thereby cross-mixing the ingredients in a transverse direction; PA1 means for elevating the ingredients from the transfer point and depositing them to form a new windrow; and PA1 preferably, means, associated with the lateral conveyance and elevating means, for wetting the ingredients between the milling and new windrow-forming steps.
The temperature of the mass is used as a guide in controlling the frequency of turning the windrow. When the windrow is first turned, the bacteria become active and the temperature of the windrow rises, perhaps to 50.degree.-60.degree. C. When the oxygen in the mass becomes depleted, the bacteria becomes less active. The temperature then begins to drop, indicating that it is time to again turn and work the windrow.
The pre-wet cycle is generally considered complete when the mixture has been adequately subjected to the high temperatures and moisture levels required for the thermophilic bacterial process to accelerate at rapid rates. Moisture content is about 65 to 74 wt. % and any moisture added thereafter would be for maintenance requirements only. The compost's polysaccharides (cellulose and hemicellulose) will have been broken down sufficiently to make the compost mixture soft and porous and ready for the next stage of compost preparation, called phase 1. Phase 1 composting typically involves further mechanical processing to form compact rectangular windrows of compost, or "ricks" which are capable of maintaining self-supporting, vertical side walls.
It typically takes about 14 days to complete the pre-wet cycle, when practised as described.
It is desirable to reduce the duration of the pre-wet cycle. It would be particularly desirable to reduce it to less than 7 days, since the rest of the compost preparation and mushroom growing steps are based on cycles of a week or less. If the extent of blending, aeration and wetting could be improved, then one would expect to see a reduction in the duration of the pre-wet cycle. It is the objective of the present invention to reach that end.